CVT System Description - Clutches/Reverse Brake/Planetary Gear/Pulleys

CVT System Description - Clutches/Reverse Brake/Planetary Gear/Pulleys

Clutches/Reverse Brake/Planetary Gear/Pulleys

Clutches/Reverse Brake

The CVT uses the hydraulic-actuated clutches and brake to engage and disengage the transmission gears. When hydraulic pressure is introduced into the clutch drum and the reverse brake piston cavity, the clutch piston and the reverse brake piston move. This presses the friction discs and the steel plates together, locking them so they do not slip. Power is then transmitted through the engaged clutch pack to its hub-mounted gear, and through the engaged ring gear to the pinion gears.

Likewise, when the hydraulic pressure is bled from the clutch pack and reverse brake piston cavity, the piston releases the friction discs and the steel plates, and they are free to slide past each other. This allows the gear to spin independently on its shaft, transmitting no power.






Clutches/Reverse Brake/Planetary Gear/Pulleys (cont'd)

Start Clutch

The start clutch engages/disengages the secondary drive gear, and is located at the end of the driven pulley shaft. The start clutch is supplied hydraulic pressure by its ATF feed pipe within the driven pulley shaft.

Forward Clutch

The forward clutch engages/disengages the sun gear, and is located at the end of the drive pulley shaft. The forward clutch is supplied hydraulic pressure by its ATF feed pipe within the drive pulley shaft.

Reverse Brake

The reverse brake locks the planetary carrier in R, and is located inside the intermediate housing around the planetary carrier. The reverse brake discs are mounted to the planetary carrier and the reverse brake plates are mounted on the intermediate housing. The reverse brake is supplied hydraulic pressure by a circuit connected to the internal hydraulic circuit.

Planetary Gear Train

The planetary gear train is only used to switch the rotational direction of the pulley shafts in R. The planetary gear train consists of the sun gear, the planetary pinion gears, and the ring gear. The sun gear is connected to the input shaft with splines. The pinion gears are mounted on the planetary carrier. The planetary carrier is located on the end of the input shaft, over the sun gear. The ring gear is located in the planetary carrier, and connected to the forward clutch drum. The sun gear inputs the engine power via the input shaft to the planetary gears, and the carrier outputs the engine power.

In D, S, and L (forward range), the pinion gears do not rotate and revolve around the sun gear, so the carrier rotates. In R (reverse range), the reverse brake locks the planetary carrier, and the sun gear drives the pinion gears to rotate. The pinion gears rotate, but do not revolve around the sun gear. The pinion gears drive the ring gear in the opposite direction from the rotational direction of the sun gear.

Pulleys

Both pulleys consist of a movable face and a fixed face, and the effective pulley ratio changes with engine speed. The drive pulley and the driven pulley are linked by the steel belt. To achieve a low pulley ratio, high hydraulic pressure works on the movable face of the driven pulley and reduces the effective diameter of the drive pulley, and a lower hydraulic pressure works on the movable face of the driven pulley to eliminate the steel belt slippage. To achieve a high pulley ratio, high hydraulic pressure works on the movable face of the drive pulley and reduces the effective diameter of the driven pulley, and low hydraulic pressure works on the movable face of the drive pulley to eliminate the steel belt slippage.